> Hello,
>
> I created a simple scene with sphere inside a room and rendered this with
>
> 1) POV-Ray
> 2) Mental Ray
>
> These are the results:
>
> 1) http://www.theoinf.de/pp/test_pov.png
> 2) http://www.theoinf.de/pp/test_mr.png
>
> I used radiosity with default settings for POV-Ray and photon mapping for 
> Mental
> Ray (10000 photons). Light attenuation follows an inverse-square-rule in 
> both
> settings (POV-Ray: fade_power 2, Mental Ray: photometric light, 700 cd). 
> All
> material is 50% grey and 100% diffuse.
>
> The image generated by POV-Ray looks less realistic than the one made by
> Mental-Ray. I was not able to improve realism by tweaking radiosity 
> settings.
>
> In theory, radiosity should work as well as photon mapping in this scene. 
> Is
> there a way to get better results with POV-Ray?

1) The default settings for radiosity in POV are intentionally low-quality,
the reasoning for this is so that they can be used to quickly preview
object placement in test renders.

2) Diffuse values in POV control the contribution of simulated
diffuse light in the normal lighting model. In situations where
standard light sources are used in conjuction with radiosity it doesn't
make sense to set diffuse to 100%, the contribution from the light
source is not 0%, the image will saturate.

3) It is common to use high ambient objects for light sources instead
of normal light sources in POV radiosity scenes. Also the standard
light sources can be used for soft shadows in POV, with or without
radiosity.

4) This is a common question, essentially comparing some typical
feature, with typical settings in some other renderer to a similar
scene in POV with atypical "noob" settings.  POV has a very good
manual, try section 2.3.7 if you really are interested in radiosity.

http://s201.photobucket.com/albums/aa280/Zakardis/?action=view&current=pov_rad_test.png

#include "colors.inc"

global_settings {
   assumed_gamma 2.2
   radiosity {
      brightness 3
      count 100
      error_bound 0.15
      gray_threshold 0.0
      low_error_factor 0.2
      minimum_reuse 0.015
      nearest_count 10
      recursion_limit 5
      adc_bailout 0.01
      max_sample 0.5
      media off
      normal off
      always_sample 1
      pretrace_start 0.08
      pretrace_end 0.01
   }
}

camera {
   location <0, 1, -4>
   look_at  <0, 1,  0>
   angle 75
}

light_source {
   <1, 4, 0>
   color 0.5*White
   fade_distance 30
   fade_power 2
   area_light <0.5, 0, 0>, <0, 0, 0.5>, 5, 5
   adaptive 1
   jitter
}

// Scene
sphere {
   <0, 1, 0>, 1
   texture {
      pigment {
         color rgb <0.5, 0.5, 0.5>
      }
      finish {
         ambient 0
         diffuse 0.6 // default diffuse setting
      }
   }
}

box {
   <-5, 0, -5>, < 5, 5,  5>
   texture {
      pigment {
         color rgb<0.5, 0.5, 0.5>
      }
      finish {
         ambient 0
         diffuse 0.6 // default diffuse setting
      }
   }
   inverse
}

Post a reply to this message